user: defer file.Close after checking for errors
api: return 409 when key already exists

Fix #61.
user: simplify string formatting
api: gofmt -s -w .
webserver: use ReadAndWatchConfigFile instead of ReadConfigFile

So we can change gandalf setting without restarting it :-)
Update setup/install.sh

update "git daemon" param
authors, contributors: add Michael (@hfeeki)
docs: fixe the create user api usage.
docs: simplifying the quickstart and the first conf.
docs: added initial docs about configuration.

Related to #63.
docs: added initial docs about configuration.

Related to #63.
fixed tests.